Integration of LVM with Hadoop

In this article we will:

  1. Integrate LVM with Hadoop and Provide Elasticity to DataNode Storage.
  2. Increase or Decrease the Size of Static Partition in Linux
  3. Automate the LVM Partition using Python-Script.

LVM

LVM, or Logical Volume Management, is a storage device management technology that gives users the power to pool and abstract the physical layout of component storage devices for easier and flexible administration. The main advantages of LVM have increased abstraction, flexibility, and control. Logical volumes can have meaningful names like “databases” or “root-backup”. Volumes can be resized dynamically as space requirements change and migrated between physical devices within the pool on a running system or exported easily. LVM also offers advanced features like snapshotting, striping, and mirroring.

Physical Volume (PV)

Physical block devices or other disk-like devices (for example, other devices created by device-mapper, like RAID arrays) are used by LVM as the raw building material for higher levels of abstraction. Physical volumes are regular storage devices. LVM writes a header to the device to allocate it for management.

Volume Group (VG)

LVM combines physical volumes into storage pools known as volume groups. Volume groups abstract the characteristics of the underlying devices and function as a unified logical device with a combined storage capacity of the component physical volumes.

Logical Volume (LV)

A volume group can be sliced up into any number of logical volumes. Logical volumes are functionally equivalent to partitions on a physical disk, but with much more flexibility. Logical volumes are the primary component that users and applications will interact with.

1. Integrate LVM with Hadoop

  • Attach Harddisks to You System.
    I added /dev/sdb (10 GiB) and /dev/sdc (15 GiB)
  • Check if they are attached.
    “fdisk -l”
  • Create Physical Volumes (PVs) from the attached Hard Disks.
    “pvcreate <hardisks>”
  • See Created Physical Volumes (PVs).
    “pvdisplay”
  • Create Volume Group (VG) from Physical Volumes (PVs).
    “vgcreate <name> <PV’s Paths>”
  • See Volume Groups.
    “vgdisplay <name>”
  • Create Logical Volume (LV) from Volume Groups.
    “lvcreate — — size <size> — — name <lv-name> <vg-name>”
  • Format the Partition (Logical Volume).
    “mkfs.ext4 <lv path>”
  • Mount the Partition (Logical Volume).
    “mount <lv path> <mount point>
  • Check the mount points.
    “lsblk”
  • Configure Hadoop with Data Node Directory as the Above used Mount Point.

Changing Size of Static Partition in Linux

On the fly, we can increase/decrease the storage to be contributed to namenode without unmounting or stopping any services.

We can see size of datanode initially is 12 GiB

  • Extend the volume.
    “lvextend — — size <size> <lv path>”
  • Format the Extended Path.
    “resize2fs <lv path>”

Now we can see the size is 17 GiB as we increased 5 GiB.

We can similarly also reduce the size on the fly.

Note: I did this task on AWS, we can also do it on our local virtual machine.

Python Script to Automate LVM

This Python Script can:
1. Display Disks
2. Display Mount Points
3. Display Physical Volumes(PVs)
4. Display Volume Groups(VGs)
5. Display Logical Volumes(LVs)
6. Create Physical Volume(PV)
7. Create Volume Group(VG)
8. Create a Logical Volume(LV)
9. Mount the Partition
10. Format the Partition
11. Resize Logical Volume(LV) (Reduce and Extend)
12. Resize Volume Group(VG) (Reduce and Extend)
13. Remove Logical Volume(LV)
14. Remove Volume Group(VG)
15. Remove Physical Volume(PV)
16. Run Custom Linux Command

LVM_Automate.py

from os import system
import getpass
def head(title=""):
system("clear")
print("-"*140)
print("Automating LVM By Karan Agrawal".center(140))
print("-"*140)
if title:
print(title.center(140))
print("-"*140)
def body():
head()
print("\n")
print("-"*140)
print("+","-"*138,"+",sep="")
text="""
Choose what you want to do:
1. Display Disks
2. Display Mount Points
3. Display Physical Volumes(PVs)
4. Display Volume Groups(VGs)
5. Display Logical Volumes(LVs)
6. Create Physical Volume(PV)
7. Create Volume Group(VG)
8. Create Logical Volume(LV)
9. Mount the Partition
10. Format the Partition
11. Resize Logical Volume(LV) (Reduce and Extend)
12. Resize Volume Group(VG) (Reduce and Extend)
13. Remove Logical Volume(LV)
14. Remove Volume Group(VG)
15. Remove Physical Volume(PV)
16. Run Custom Linux Command
0. Exit
"""
for i in text.split("\n"):
print("| ",i.center(136)," |",sep="")
print("+","-"*138,"+",sep="")
choice=input(">>> ")
return choice
def tasks(ch):
global kk
if ch == '1':
head("Display Disks")
system("fdisk -l")
elif ch == '2':
head("Display Mount Points")
system("df -hT")
elif ch == '3':
head("Display Physical Volumes(PVs)")
pv = input("Enter name of the PVs or Press Enter to view all PVs\n>>> ")
system("pvdisplay "+pv)
elif ch == '4':
head("Display Volume Groups(VGs)")
vg = input("Enter name of the VGs or Press Enter to view all VGs\n>>> ")
system('vgdisplay '+vg)
elif ch == '5':
head("Display Logical Volumes(LVs)")
lv = input("Enter name of the LVs or Press Enter to view all LVs\n>>> ")
system('lvdisplay '+lv)
elif ch == '6':
head("Create Physical Volume(PV)")
pv=input("Enter location of the PV\n>>> ")
system("pvcreate " + pv)
elif ch == '7':
head("Create Volume Group(VG)")
vg=input("Enter the name of the VG\n>>> ")
nopv=(input("Enter the Name of PVs (Seprated by Space)\n>>> "))
system("vgcreate " + vg +" " + nopv)
elif ch == '8':
head("Create Logical Volume(LV)")
lv = input("Enter the name of LV\n>>> ")
size=input("Enter the size of LV\n>>> ")
vg=input("Enter the name of VG\n>>> ")
system("lvcreate --size {} --name {} {}".format(size,lv,vg))
elif ch == '9':
head("Format the Partition")
lv = input("Enter the name of LV\n>>> ")
vg=input("Enter the name of VG\n>>> ")
system("mkfs.ext4 /dev/{}/{}".format(vg,lv))
elif ch == '10':
head("Mount the Partition")
lv = input("Enter the name of LV\n>>> ")
vg=input("Enter the name of VG\n>>> ")
path=input("Enter Folder you want LVM to mount upon\n>>> ")
system("mkdir -p "+path)
system("mount /dev/{}/{} {}".format(vg,lv,path))
elif ch == '11':
head("Resize Logical Volume(LV) (Reduce and Extend)")
c = input("Reduce/Extend LV (R/E)\n>>> ").upper()
vg = input('Enter name of VG\n>>> ')
lv = input('Enter name of LV\n>>> ')
if c == 'E':
c='extend'
s='+'
size = input('Enter Size by which you want to extend LV\n>>> ')
system('lv{} --size {}{} /dev/{}/{}'.format(c,s,size,vg,lv))
system('resize2fs /dev/{}/{}'.format(vg,lv))
elif c== 'R':
size = input('Enter size by which you want to change LV size\n>>> ')
size2 = input('Enter the final reduced size of LV desired\n>>> ')
path = input('Enter Mounting Point of LV\n>>> ')
c='reduce'
s='-'
system('umount /dev/{}/{}'.format(vg,lv))
system('e2fsck -f /dev/{}/{}'.format(vg,lv))
system('resize2fs /dev/{}/{} {}'.format(vg,lv,size2))
system('lv{} --size {}{} /dev/{}/{}'.format(c,s,size,vg,lv))
system('mount /dev/{}/{} {}'.format(vg,lv,path))
else:
print("Invalid Choice")
elif ch == '12':
head("Resize Volume Group(VG) (Reduce and Extend)")
c = input("Reduce/Extend VG (R/E)\n>>> ")
vg = input("Enter name of the VG\n>>> ")
pv = input("Enter name of the PV\n>>> ")
c=c.upper()
if c == 'E':
system("vgextend {} {}".format(vg,pv))
elif c == 'R':
system('pvmove {}'.format(pv))
system('vgreduce {} {}'.format(vg,pv))
else:
print("Invalid Choice")
elif ch == '13':
head("Remove Logical Volume(LV)")
path = input('Enter LV you want to remove\n>>> ')
system('umount {}'.format(path))
system('lvremove {}'.format(path))
elif ch == '14':
head("Remove Volume Group(VG)")
vg = input('Enter VG you want to remove\n>>> ')
system('vgremove {}'.format(vg))
elif ch == 15:
head("Remove Physical Volume(PV)")
path = input('Enter PV you want to remove\n>>> ')
system('pvremove {}'.format(path))
elif ch == '16':
head("Running Linux Command")
cmd=input("Enter command you wanna run\n>>> ")
system(cmd)
elif ch == '0':
head("Exitting")
kk=False
else:
head("Invalid Choice Try Again!!!")
head("Welcome...!Press any key to start configuring LVM")
input()
kk= True
while kk:
tasks(body())
input()
head("Thank You")

For the Github link, click here.

Done with the help of:
- Arunava Mitra
- Tejas Sanghai